This invention relates to a data slicing apparatus and method.
Data slicing is a process whereby the incoming signal is compared with a reference level such that should the incoming signal exceed the reference level, the data slicer produces an output in one sense and should the input signal be less than the reference level the data slicer produces an output in the opposite sense. Hence the action of the data slicer is to reconstruct from the incoming signal the original information. The establishment of the correct level about which the data slicer operates is important since the presence of various distortions in the incoming signal will mean that the data signal is no longer symmetrical about any specific reference level.
In television systems it is known to transmit digital data on one or more `lines` of the video signal. Transmission of digital data along with the normal picture information forms the basis of the operation of teletext systems, e.g. CEEFAX and ORACLE. In the known systems, the incoming video waveform is referred to a fixed voltage level and the data is "sliced" by means of a device which compares the incoming data waveform with a voltage level which bears a fixed relation to the reference level. With such systems, distortions etc., results in the chosen relationship being incorrect and hence the data can be incorrectly sliced and thus impaired or lost.